Megagrip Liquid Chalk everytime (myprotein's is just relabelled Megagrip). A bottle lasts an absolute age, and during a session once I've chalked up my whole hand I'll only have to occasionally redo my fingertips where the chalk's been worn off by loading plates, tightening my belt etc, and for that only a tiny little drop is needed (about the size of a chocolate chip, or a rat's nose). Plus it doesn't make the platform slippery, or clog up the bar knurling. I only use regular block chalk now when I'm back in Leeds and don't have all my kit with me.
“Begin at the beginning,” the King said gravely, “and go on till you come to the end. Then stop.”